Report Due Today on Sandy Hook Shooting Investigation

Investigators are planning to release a long-awaited report on the Connecticut school shooting, nearly a year after the massacre of 20 children and six women inside Sandy Hook Elementary School.

A memorial for those killed in the school shooting at Sandy Hook Elementary School (Andrew Burton/Getty Images)

The summary report by the lead investigator could provide some of the first official answers to questions about the history of the gunman and the police response to one of the worst school shootings in American history.

The Dec. 14 shooting plunged the small New England community into mourning and led states across the country to re-evaluate gun laws.

The report expected Monday afternoon won't include state police's full evidence file, which is believed to total thousands of pages. The decision to continue withholding the bulk of the evidence is stirring new criticism of the secrecy surrounding the investigation.